1. Field of the Invention
This invention relates to improvements in and relating to heaters and more particularly to a heater casing formation which can provide "visual flame" characteristics.
2. Description of the Prior Art
"Visual flame" characteristics enable the burning fuel to be seen from outside the heater usually through a transparent or translucent portion of the heater. Open fires are in the main inefficient in converting solid fuels to useful heat, are expensive and difficult to install in a building and can be the cause of dirt, dust and smoke in a building.
So called enclosed solid fuel burning appliances, such as those with a fire chamber assembly, controlled air inlet and controlled combustion can provide very efficient burning of fuel, (for example coal, coke, timber and the like), however, many are unable to satisfactorily provide the desirable "visual flame" characteristics of an open fire.
Attempts have been made to meet the problem of providing an enclosed solid fuel burning appliance having "visual flame" characteristics by providing a small viewport or glass window, typically, in a front door of the fire chamber assembly. However, various problems have been experienced with such configurations, including cracking of the viewport both due to mechanical and thermal effects as well as obscuring of the glass by soot, smoke and products of fuel combustion.
Particularly the viewport tends to become obscured by condensation deposits forming on an inner face of the viewport, those deposits subsequently become burnt on in the manner of a sticky deposit, to which dust and smoke particles adhere. Creosote is one of the deposits often left when burning timber.
Various elaborate means have been devised in attempts to provide a non-cracking and clean viewport, such as the provision of a buffer zone of clean inlet air between the viewport and the fuel or fire, however, while a few of these structures have been successful on a small viewport, heaters have the appearance of an enclosed stove with a "port hole" through which the fire can be viewed. This is regarded by the applicant as less than desirable.
Most, if not all solid fuel heating arrangements require a non combustible and insulating floor protector, to reduce the likelihood of damage to a floor or floor coverings in front of the apparatus to reduce the deleterious effect of radiant heat in that area. Traditionally, the floor protector is provided by means of a hearth. Where there is a viewport, there is an increased possibility of heat radiating from the appliance and therefore, there is a need for the floor protector to be somewhat thicker and larger than the applicant considers desirable. This can cause obstruction, can lead to a restriction in convenient placement of the heater and is also expensive.
When not in operation the interior of the fire chamber of a solid fuel heating means is readily visible, either through the fire opening in the case of an open fire, or through a viewport in the case of a ported enclosed solid fuel stove. This is less than desirable, aesthetically. Attempts have been made to provide a visual screen to obscure the interior of the fire from view however, these have been essentially mechanical in their arrangement and have led to increased costs, maintenance problems and in some cases the screens have been difficult to use.
In operation of an enclosed solid fuel heater, there is, furthermore, a natural conflict of requirements. In the first instance, it is desirable for efficient burning of the fuel in the fire chamber for the interior of the fire chamber (including the surfaces of the fire chamber) to be as hot as possible so as to achieve efficient pyrolisis and furthermore, to burn off any creosote deposits which have formed on the inside of the fire chamber or to prevent creosote and other deposits of combustion forming thereon.
It is furthermore desirable for at least the outside portions of the heater exposed where they can be touched to be as cool as possible to reduce the likelihood of injury or damage of the viewport due to thermal shock and the like. Historically, there have been substantial difficulties in achieving the required compromise and as operation of the heater is the more important requirement, there has been a tendency for the outer exposed surfaces of the fire chamber to be somewhat hotter than is desirable or safe, especially when the heater is in high output mode.